Marble Hill-225 Street is located at the northern end of the Broadway Bridge that the 1 train and crosses above Broadway, but is still technically within the confines of Manhattan even though the area is now physically connected to the Bronx. This is because the Broadway Bridge doesn't technically go over the Harlem river, but the Harlem Ship Canal, before that canal was built the Harlem River was reduced to a narrow stream as it went around the area called Marble Hill today, the ship canal was built to allow ships to pass, and the smaller river that was formerly making Manhattan an island was filled in and this tiny portion of Manhattan has been taken away from the rest of it and attached to the mainland. That is where this subway station is. Deep below the station reached by a long staircase down to it on the banks of the Harlem River is Metro-North's Hudson Line and the Marble Hill Station, that is a quite well used subway transfer point.
The design of the station itself is a regular Broadway elevated station with two side platforms on the three-tracked line. The canopied areas are towards the southern end of the platform where the exits are to either side of Broadway and 225 Street, the downtown platform has a small station house with fare control alongside the platform, and staircases down to either side of Broadway. The uptown platform just has two staircases one of which ends at a High Entrance/Exit Turnstile to allow people to board uptown trains, the opposite one is an exit only High Exit Turnstile.

(225n11) A 1 train about to go over the Broadway Bridge.
Photo by Jeremiah Cox, 21 December, 2003.

(225n12)(225n14) R33-ML #9017 leads the SMEE train of many colors on a fan trip makes it's way up the center track of the Broadway Line and over the Broadway bridge and poses at 225 Street-Marble Hill.
Photo by Jeremiah Cox, 25 April, 2004

(225n15)(225n16) A R62A 1 train enters 225 Street-Marble Hill passing R33-ML #9017 that leads the SMEE train of many colors on a fan trip that is stopped on the center track at 225 Street.
Photos by Jeremiah Cox, 6 April, 2004